1. Field of the Invention:
This invention relates to an information signal reproducing apparatus and, more particularly, to an apparatus arranged to reproduce information signals from a recording medium on which many recording tracks are formed in parallel to each other.
2. Description of the Related Art:
The rotary head type magnetic video recording or reproducing apparatus using a magnetic recording tape (hereinafter referred to as VTR for short), as well known, generally has two tape speed operating modes. One is a long time recording or reproducing mode (hereinafter referred to as LP mode) and the other is a standard recording or reproducing mode (hereinafter referred to as SP mode). If the VTR of this kind is arranged to perform recording and reproduction with the same pair of rotary heads both in the LP and SP modes, there arises the so-called guard band in the case of the SP mode because the SP and LP modes give different spacing distances between recording tracks from each other as shown in FIGS. 1 and 2 of the accompanying drawings, the former showing the tracks formed by the LP mode and the latter the tracks formed by the SP mode. As a result, in the SP mode, the pair of heads are unable to pick-up pilot signals simultaneously from two tracks neighboring a track which is mainly under control (hereinafter referred to as the main track) in accordance with the known four-frequency pilot control method. Therefore, with the VTR arranged in the above-stated manner, it has been hardly possible to accurately carry out the tracking position control over the head 13 and the pattern of the track 12. The further details of this are as follows:
Referring to FIGS. 1 and 2, the illustrations include a magnetic tape 11 which is employed as a recording medium; recording tracks 12 in which signals are recorded; a head 13; and the above-stated guard band 14.
FIG. 3 shows a tracking error signal 18 obtained from pilot signals reproduced from the two neighboring tracks together with the RF output level of information signal or a pilot signal output level 17 of the information signal reproduced from the main track in relation to the deviating degree 16 of the head 13 from the center of the track. The deviating degree 16 is on the axis of abscissa and the reproduction output level 19 of the head 13 on the axis of ordinate. The tracking error signal 18 has a dead zone corresponding to the width of a guard band 14 if the tape 11 has the guard band. In other words, the error signal output becomes zero while the reproducing head 13 is within this dead zone. Under that condition, even if the level 17 of the RF output or that of the pilot signal reproduced from the main track is caused to become lower than a maximum value by the deviation of the center of the reproducing head 13 from the center of the track, no control is performed on the travel of the tape. In the event of deviation of the head 13 to a greater extent from the center of the track, no control can be accomplished until the tracking error signal 18 comes to be reproduced from the neighboring tracks. In that event, the travelling position of the tape 11 is adjusted to an inapposite position determined by the characteristic of a tape travelling speed control system.